Steps for Performing an ALT Analysis
The purpose of ALT analysis is to determine the relationship between the reliability and life span of the product or system based on accelerated component aging. To perform ALT analysis, you insert data sets in the System file and supply collected data points. You then specify the parameter values to use in the analysis.
This topic provides guidance on the steps you take to effectively and efficiently perform ALT analysis. In addition to supplying general instructions and descriptions, this topic references other topics where appropriate. These referenced topics typically describe how to perform the actions indicated.
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The actions in the following table are numbered to indicate that they are performed sequentially. For accurate analyses, you must complete these actions in the order in which they are listed.
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Action
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Description
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1.
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Define the conditions of the failure mode to analyze and determine the failure usage scale.
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For the failure mode to analyze, clearly define the conditions that cause this failure to occur and the failure usage scale by which product or system age is measured. This task, performed outside of the software, determines what failure data must be collected.
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2.
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Open or create the System file and then insert data sets.
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A data set is inserted in the LDA Navigator for each collection of data points to analyze. To analyze many data sets with different distributions, you can first insert data set folders to better organize and manage them. For more information, see:
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3.
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If stress is to vary over time, insert stress profiles.
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Stress profiles are special data sets that indicate how stress levels vary over time. For more information, see Stress Profiles.
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4.
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For an ALT data set, specify parameters and stress data.
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For an ALT data set, parameters and stress data affect the table columns shown in the ALT Data Points pane. For more information, see ALT Parameters Pane for an ALT Data Set.
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5.
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Enter the data points to analyze.
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The data points to analyze are entered in the ALT Data Points pane. For more information, see ALT Data Points Pane for an ALT Data Set.
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6.
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Specify the distribution and parameter values to use.
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For an ALT data set, you specify the distribution, parameter values, and stress data in the ALT Parameters pane. If you do not know the distribution, you can use best fit distribution analysis to determine which of the three supported distributions best fits the data points. You do this for an ALT data set in the same manner as you do for a parametric life or warranty data set in the Weibull module. For more information, see Finding the Best Fit Distribution for a Data Set.
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7.
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Calculate the data set and view results and generated plots.
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By default, Auto-Calculate data sets is cleared under ALT in the System file properties. In this case, you must initiate calculation of a ALT data set, which you can quickly do by clicking Calculate in the title bar of the ALT Parameters pane. If you select Auto-Calculate data sets for this module, an ALT data set is calculated as you enter data and parameter values. This checkbox applies only to a standard ALT data set. For an accelerated degradation data set, you must click Calculate in the title bar of the ALT Parameters pane. Or, to calculate it or all data sets for this module, you can press F8 or click Calculate in the standard toolbar. For more information, see Calculating ALT Results. Once a data set is calculated, you can view generated plots in the ALT Plot pane. If the plots indicate that your initial parameter values do not provide a good fit, you can change them and recalculate. Once plots indicate that parameter values are acceptable, you can use the resulting analysis to spot trends in the data set and accurately estimate future failures.
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8.
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Generate ALT reports.
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Generate ALT reports. No Graph Template files are supplied with this module, and the Graph Wizard does not support the creation of Graph Template files for it.
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